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• Use of forces to precisely position chromophores:Noncentrosymmetric ordering required.Dipole-dipole interactions oppose this ordering. Poling and Steric Forces must be used to minimize

undesired effects of dipole-dipole interactions.

• Uniform chromophore array (and high concentration) necessary:Maximizes electro-optic activity.Avoids optical loss from scattering due to density variations.

• Achieving nanostructured electro-optic materials: 1. Electric field poling of dendritic materials.2. Sequential (layer-by-layer) synthesis from an appropriate

substrate (which also serves as a cladding material). 3. Ferro-electric structures.

Why Nanostructured Electro-Optic Materials?

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Quantum Mechanics

H = E

Levels of Theory: 1st PrinciplesT

ime

Distance

femtosec

picosec

nanosec

microsec

seconds

minutes

hours

years

1 Å 1 nm 10 nm micron mm meters

Mesoscale Dynamics

Segment AveragesGroup AdditivitiesSolubilities

Molecular Dynamics

F=MA

Force Field Charges

Finite Element Analysis

Process Simulation

Equilibrium PropertiesTransport Properties

E & M Response and Properties

Engineering Design

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Theoretically inspired rational improvement of organic electro-optic materials

Theories (quantum and statistical mechanics) have guided the systematic improvement of the hyperpolarizability () of organic chromophores and the electro-optic activity of macroscopic materials.

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N NO2R

R

N NR

R

N NO2

N

R

R

SN

OO

Ph

ISX

N

R

R

S CN

NC

CF2(CF2)5CF3

N

R

R

NO

O

Ph

FCN

APTEI

N

R

R

S

NC

CN

NC

CN

TCI

N

R

R

S CN

NC

CN

N

R

R

S CN

NC

CN

TCV

N

R

R

S SO2

NC

CNTCVIP

SDS

N

R

R

SO

NCCN

NC

N

R

R

O

NCCNNC

R'

NA

DR, 30 wt%, r33 = 13 pm/V

FTC, 20 wt%, r33 = 55 pm/V

CLD

(x10-48 esu)

80

580

2,000

3,300

4,000

6,100

(x10-48 esu)

9,800

13,000

15,000

18,000

30,000

Systematic Improvement in Molecular Electro-Optic Activity: Variation of mb

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Driven by Quantum MechanicalCalculations of Molecules ThatCan Be Synthesized & Processed

Hyperpolarizability (b)

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r eff in absence of intermolecular

interactions

34

cosn

NFreff

Figure of Merit

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.

New Strategy:Gradient-Bridge, Mixed-Ligand-Acceptor Chromophores

•Quantum mechanical calculations permit the optimization of the -electron structure that defines molecular hyperpolarizability. •Microwave synthesis techniques permit dramatic enhancement in reaction yields and synthesis of new materials.

N

SS

N

N

N

HO

OH

O

D D

C

B

A

A, B, C = NO2, CN, SO2CF3, etc.

D = CF3, etc.

New Advances in Chromophore Development

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.

•Microwave synthesis has permitted dramatic enhancement in reaction yields, reducing time devoted to purification. It has also permitted many materials to be synthesized for the first time and has permitted greater flexibility in reaction conditions.

•Microwave synthesis techniques obviously permit more uniform heating of reaction mixtures. The absence of thermal gradients and “hot spots” helps minimize decomposition and side reactions. Microwave synthesis permits the use of a wider range of solvents.

•We have found this approach to be particularly effective for condensation, addition, and de-protection reactions.

Why Microwave Synthesis?

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Comparison of Microwave and Reflux Synthesis of CF3-TCF acceptor

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.

O

OH+

CN

CN

Microwave 20 W

EtONa/EtOH O

CN

NH

O

CN

NH+

CN

NO2

Microwave 20 W

EtONa/EtOHO

CN

CN

NO2

+CN

COOEt

Microwave 20 W

EtONa/EtOHO

CN

CN

COOEt

O

CN

NH+

Microwave 20 W

EtONa/EtOHO

CN

N

NO

O

S

Et

EtN

N

O

O

Et

Et

S

12

1 3

14

O

OH+

CN Microwave 20 W

EtONa/EtOH O NHN

N

+CN

CN

Microwave 20 W

EtONa/EtOH O

N

CN

CN

5 6

O

CF3

OH+

CN

CN

Microwave 20 W

EtONa/EtOH O

CN

NHF3C

+CN

CN

Microwave 20 W

EtONa/EtOHO

CN

F3C

CN

CN

78

Examples of Microwave Synthesis

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.

NBu

Bu

S O

O

CN

CN

CNF3C

, 20W, 8 min.N

Bu

Bu

S O

NCCN

CN

CF3

OTBDMS

OTBDMSEtOH

NBu

Bu

S O

O

CN

CN

CNF3C

EtOH, reflux

NBu

Bu

S O

NCCN

CN

CF31.5 hr.

NBu

Bu

O

NC

CF3

NC

CN

NBu

Bu

O+

O

CN

CN

CNF3C

cat. Py. Piper.

THF, CHCl3, reflux

NBu

Bu

O

NC

CF3

NC

CN

NBu

BuO

CN

CN

CNF3C

cat. Py. Piper.

THF, CHCl3, reflux

O

+

LMAJ 22

LMAJ 24

1

2

Coupling Reactions

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0.85 dB/cmat 1.55 mm

0.68 dB/cm at 1.3 mm

Perfluorodendron-substituted Chromophore Contributes Little to Optical Loss in Guest-Host APC Polymer

Reducing Optical Loss

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.

• Photochemical stability can be improved by chromophore design.

Lumera has demonstrated this.

• Photochemical stability can be improved by the use of scavengers

Photo Stability of Different FTC Samples

0

20

40

60

80

100

120

0 50 100 150 200

UV Exposure Time (minute)

Inte

ns

ity

Ra

tio

(%

)

FTC in Air

FTC Sealed

FTC w/ Quencher in Air

FTC w/ QuencherSealed

Optimizing Photostability

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1, 2, 3

1 32

Laser1, 2, 3

Modulates 1 Modulates 2 Modulates 3

Transmitter Receiver

1, 2, 3

1 32

1, 2, 3

1 32

Laser1, 2, 3

Modulates 1 Modulates 2 Modulates 3

Laser1, 2, 3

Modulates 1 Modulates 2 Modulates 3

Transmitter Receiver

dn

rnKv

V

BW

e

o

FWHM 233

3

Eye diagram1 Gb/s, Vpeak = 1 VDevice has ~2GHz BW

Au Electrode

SU-8

Gold ground

GND

= 2 GHz/V

Integrated WDM Transmitter Receiver

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Evolution of N<cos3>

Simple ChromophoreShape Modification

Loading

First Multi- Chromophore Dendrimer

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Centric Ordering

E

Chromophore-polingField Interaction

Thermal Randomization Chromophore-ChromophoreElectrostatic Interaction

Acentric Ordering Isotropic

<cos3>= F/5kT = f(0)Ep/5kT

<cos3> =(F/5kT)[1-L2(W/kT)]

34

cosn

NFreff

Translating Microscopic to Macroscopic Electro-Optic Activity

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Analytic Theories for Spheroidal Dipoles

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Monte Carlo Calculations

• Use Monte Carlo methods to determine the effect of dipolar interactions between chromophores.

A 5 by 5 two dimensional array

Randomly oriented dipoles

• Place dipoles on a grid (simple cubic lattice and body centered cubic lattice)

• M by M by M array with r as nearest neighbor distance.

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How Monte Carlo Works

• Choose a dipole

• Rotate dipole by: a rotation axis and angle, selected randomly

• Compare the energy before and after rotation.

If the energy is lower, keep the

move

If the energy is higher, compare Boltzmann

Probability with a [0,1] random number, and keep if

larger.

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Comparison of Potential Functions from Analytic Theory & Monte Carlo Calculations

Solid Line—Analytic Theory

2 22 2

3

Nw s s

r kT kT

.

0.3 cosexp wP A

Points—Monte Carlo Calculation

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.

Prediction of the Dependence on Poling Field

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Comparison of Theory & Experiment

.

Experiment—SolidDiamonds

2max 2 2

0.48 0.28 4.8 kT kT

N f

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Lattice Geometries

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.

New Strategy: Generalize the Concept of Dendronized Chromophores.

: Dendritic moiety

: Polymer backboneCore moiety

: NLO chromophore moiety

: Crosslinkable moiety:

x yx y

Side-Chain dendronized NLO polymer

Dendritic NLO chromophore

NLO dendrimer

Dendrimer Synthesis

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NS

S

O

NC

CN

NC

R

R

DMC3-97

NLO Chromophre

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Features of Ellipsoids• Complete flexibility of Charge and Dipole Distributions

• Complete flexibility of Connectivity to other Ellipsoids

• Complete flexibility of oreintation (for Monte Carlo and Brownian Dynamics Trajectories)

• Polarizability Tensor

• Computes all electrostatics with other Ellipsoids and arbitrary External Field

• A contact function to find Ellipsoid-Ellipsoid interactions

• Can have either Hard-Shell Repulsion or Leonard-Jones Interactions

• Solvent free energies and exposure factors (use the rolling ball method)

• Can generate dendrimers, polymers and lattices of ellipsoids

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Dendrimer Performance

Statistical Mechanical Theory explains the improved performance of dendritic chromophores.

O

O

OO

O

ON

S

CNNC

NC

NC

O

O

O O

FF

OF

O

O

FF

OF

O

N

S

NCCN

NC CNO

O

O

OF

F

O

FO

OF

F

O

FO

NS

NCCN

CN

CN

O

O

OO

F F

O F

O

O

F F

O F

O

O

O

O

By choosing a tilt

angle for the three chromophores (~60°) the experimental enhancement (of ~ 2 fold) was realized.

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Dendrimer Structure

Original Geometry

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Three-Fold Dendrimer

Three chromophores at Equilibrium

With NO poling field: Nearly Planar

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Three-Fold Dendrimer

Three chromophores at Equilibrium

With a poling field: Constrained and Aligned

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Polymer of Dendrimers

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Lattice of Dendrimers

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Thermal Annealing

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Aspect Ratio: A Search for more order

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Aspect Ratio and Field

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Mission Possible Materials (I)

• The state of the art for OEO Materials:R33: 70 pm/V (CLD in 2000) Vp: 0.8 V (2000)

R33: 130 pm/V (2002) Vp: 0.3 V (2000)

• Industry Standard: LiNiO3

R33: 32 pm/V Vp: 5 V (@40 GHz)

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Mission Possible Materials (II)

• Quantum Mechanical Based Improvements:

Increase b : Yes, by 5-10 fold

Placement of Heteroatoms; Mix Donors and Acceptors

Increase m: No, not needed Already 20 Debye and will go higher anyway

• Statistical Mechanical Based Improvements:Improve order by 5 fold (currently order is 5%)

o Design Dendrimers o Improve Steric Interactionso Place Chromophores on Polymer Backbone

Improve order 20 fold o FerroElectrically ordered materials

Only Theory can begin to crack this problem.The new R33 is 130*20 = 2600 pm/V

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Mission Possible Materials (III)

• Engineering Based Improvements:

BandWidth: Done (100+ GHz performance now)

Devices are cladding limited

Design Devices to be in Resonant Structures

(Trade Bandwidth for Vp)

Use Photonic Band-Gap Structures to obtain beam confinement and minimize the need for cladding.

(Theory can predict light beam confinement)

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Light Through Regular Array

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Light Beam in Photonic Material